Thanks for the article. I've recently inherited a number of SQL Servers, so have had to give this some thought.

Here's a few additional items...

Has a recent DBCC CHECKDB been run on every database? If not, do so ASAP.

Examine the current logs (SQL Server, Windows) on the server. Any problem areas ?

See what features are enabled under Surface Area Configuration

Find out what client libraries are in use. If IP, does SQL Server listen on a non-default port (For security, hopefully, yes!) From my experience, use of an incorrect port is the cause of a majority of client connectivity issues